The development of the Internet is more and more making possible exchanges of messages electronically. Current technology has made possible the development of the digital image and the transfer of the images by means of a network such as for example the Internet. Currently, recent cellular telephones are provided with a screen which makes it possible to display messages. Such screens, for the moment, have only a few density levels and a small number of display pixels, in general around 96×44. Obviously colour screens are beginning to appear. Because of this, the number of colours which can be displayed is still relatively low. Under these circumstances, the direct display of a colour image of relatively high definition on this type of screen cannot be exploited visually and is of little advantage.
There is therefore a need for a device and method for displaying a monochrome representation, or one with a small number of colours, of a colour digital image on a cellular telephone screen having a small number of pixels and a small number of grey levels, possibly in each of the primary colours.
In the present application the expression “grey level” means discrete density, saturation or illumination steps or values according to the type of space concerned. This expression can even be used for colour images, each primary colour having a limited number of “grey levels”; this can also be referred to as the “depth of colour”. The expression “relatively high definition” means an image with a number of pixels of at least approximately 640×480 and a depth of colour coded in approximately 8 bits.
The invention aims to provide to a cellular telephone an item of information processed so as to optimise the information transmitted as a function of the apparatus used for receiving this information.
Another aim of the invention is to automatically provide a display of “vignettes” resulting from the traditional commercial processing of silver photographic films on a cellular telephone screen.